1. Field of the Invention
The invention relates to a mixing system for a container with flexible walls.
2. Description of the Related Art
Single-use containers with flexible walls are increasingly used in biotechnology and in the pharmaceutical industry for mixing liquids, dissolving solids in liquids or cultivating cells and microorganisms. Here, an advantage of single-use containers made of plastic is that they can already be supplied by the supplier in a clean and, where necessary, sterile state, as a result of which complex cleaning procedures and validations pre-use are dispensed with.
Rotating stirrer shafts provided with stirrer elements such as e.g. propellers are particularly suitable for effectively mixing media in single-use containers with flexible walls. In order to drive such stirrer shafts, it has proven its worth to couple the torque from the motor onto the stirrer shaft by a contactless magnetic coupling, which can be operated without wear-and-tear.
U.S. Patent Application Publication No. 2007/0053238 A1 describes a magnetic coupling for a stirrer shaft in which the drive components, such as bearings and magnets, are situated outside of the container interior. However, a disadvantage of this embodiment is that the container interior, which contains the media to be mixed, is not sealed from the drive components. Thus, the first bearing for accommodating the stirrer shaft is located directly at the opening between the container interior and the magnetic coupling. As a result of this arrangement, bearings and the magnets (drive magnets) affixed to the stirrer shaft can come into contact with the media to be mixed and can be damaged by corrosion. Conversely, it is possible for particles originating from the bearings or the magnets to reach the container interior and thus lead to a contamination of the mixture. This is all the more serious because these mechanical components are generally made of metals and can therefore not be sterilized without problems by gamma radiation.
The object of the invention therefore consists of proposing a cost-effective mixing system with a drive for a single-use container, in which the sterility of the container interior is ensured.